I don't think a smart guy would send a Eth to unknown address without double checking.
Mostly he is gonna copy paste the address anyway.
In case he sends it I think most people wouldn't send it back to him.
In general, it is not possible to know exactly who the sender is and if 1 ETH is of high value during that time, it will be very unlikely to return. I've never been in this situation, but I understand if I send it wrong it all ends and there is almost no hope of getting the money back. It is best for each person to be careful in the transaction and to check multiple times before deciding to send.